Immunological agglutination reactions are presently used for identifying various kinds of blood types as well as for detecting various kinds of antibodies and antigens in blood samples and other aqueous solutions. In such procedures, a sample of red blood cells is mixed with serum or plasma in either test tubes or microplates, wherein the mixture is incubated and then centrifuged. Various reactions then occur or do not occur depending on, for example, the blood types of the red blood cells or whether certain antibodies are present within the blood sample. These reactions manifest themselves as clumps of cells or as particles with antigens or antibodies on their surfaces, referred to as agglutinates. The failure of any agglutinates to appear indicates no reaction has occurred, while the presence of agglutinates, depending on the size and amount of the clumps formed, indicates the presence of a reaction and the level of concentration of cells and antibodies in the sample and reaction strength.
As described, for example, in U.S. Pat. No. 5,512,432 to LaPierre et al., and rather than using microplates or test tubes, another form of agglutination test method has been developed and successfully commercialized. According to this method, gel or glass bead microparticles are contained within a small column, referred to as a microcolumn or a microtube. A reagent, such as anti-A, is dispensed in a diluent in the microcolumn and test red blood cells are placed in the reaction chamber above the column. The column, which is typically one of a plurality of columns formed in a transparent card or cassette, is then centrifuged. The centrifugation accelerates the reaction, if any, between the red blood cells and the reagent, and also urges any cells toward the bottom of the column. In the meantime, the glass beads or the gel material acts as a filter, and resists or impedes downward movement of the particles in the column. As a result, the nature and distribution of the particles in the microcolumn provides a visual indication of whether any agglutination reaction has occurred, and if such a reaction has occurred, the strength of the reaction based on the relative position of the agglutinates in the column. If no agglutination reaction has occurred, then all or virtually all of the red blood cells in the microtube will pass downward during the centrifugation procedure, to the bottom of the column in the form of a pellet. Conversely and if there is a strong reaction between the reagent and the red blood cells, then virtually all of the red blood cells will agglutinate, and large groupings will form at the top of the microtube above the gel or bead matrix in that the matrix is sized not to let these clumps pass through. Reactions falling between these latter two extremes are possible in which some but not all of the red blood cells will have agglutinated. The percentage of red blood cells that agglutinate and the size of the agglutinated particles each have a relationship with the strength of the reaction. Following the centrifugation process and after all processing steps have been completed, the microtube is visually examined by either a human operator or by machine vision and the reaction between the red blood cells and the reagent is then classified. The reaction is classified as being either positive or negative, and if positive, the reaction is further classified into one of four classes depending on the strength of the reaction.
Currently, so-called gel cards and/or bead cassettes are known test elements that employ a plurality of microtubes for purposes of creating agglutination reactions as described above for purposes of blood grouping, blood typing, antigen or antibody detection and other related applications and uses. These test elements commonly include a planar substrate that supports a plurality of transparent columns or microtubes, each of the columns containing a quantity of an inert material, such as a gel material or a plurality of glass beads, respectively, that is disposed in an aqueous slurry that includes an antibody or antigen or is provided with a carrier-bound antibody or antigen, each of the foregoing being provided by the manufacturer. A pierceable wrap completes the assembly of the test element, the wrap, which may be, for example, in the form of an adhesively or otherwise-attached foil wrap, covering the top side of the test element, in order to cover the contents of each column. Once pierced, aliquots of patient sample and possibly reagents (e.g., if reagents are not first added by the manufacturer or additional reagents, depending on the test) can be added to the columns, either manually or using automated apparatus. The test element thus containing patient sample (e.g., red blood cells and sera) is then incubated and following incubation, the test element is spun down by centrifugation, as noted above, in order to accelerate an agglutination reaction that can be graded either based on the position of agglutinates within each transparent column of the test element or cassette or due to a lack of agglutination based on the cells settling at the bottom of the test column.
As noted, each of these test elements include a foil wrap disposed at the top of the card or cassette covering the columns wherein the wrap can be pierced prior to the dispense of the patient sample, reagents, or other material into at least one microtube of the test element. The foil wrap forms a seal relative to the contents of the columns to prevent contamination and also prevents the contents of the columns from drying out or degrading.
A number of automated or semi-automated apparatus, such as those manufactured by Ortho-Clinical Diagnostics, Inc., DiaMed A.G., and Grifols, are known that utilize plurality of gel cards or bead cassettes, such as those manufactured and sold by Micro-Typing Systems, Inc., DiaMed A.G., and BioRad, among others. Typically, these apparatus employ separate assemblies to accomplish the piercing function. In one known version, a pipette assembly probe is used to directly puncture the foil wrap. Using the metering probe for puncture wherein contact is made with the contents of the test columns means that this probe must undergo a separate washing operation following the piercing step before use thereof can be resumed to avoid contamination. In addition to potential contamination issues, there are also related issues dealing with spillage as well as fluidic carryover. In addition, washing operations add levels of complexity to the size and manufacture of the apparatus as well as hinder potential throughput time. In another known apparatus, a piercing assembly is provided having a plurality of dedicated puncture elements used to puncture the seals for each of the test chambers of a test element. This dedicated apparatus also adds a level of complexity, including an increase to the size of the overall footprint of the apparatus. The latter assembly also requires washing operations of the puncture elements themselves prior to any re-use thereof. Furthermore, the latter puncture assembly operates with only a fixed number of configurations wherein typically all of the test columns of the test card are punctured, even for tests in which certain columns are not necessarily required. Still other test elements are accessed by removal of the entire foil strip prior to processing.